On 6 June 2024, Microsoft 365 will remove inactive external ‘HOST’ accounts. This action applies to accounts where external users have not accepted an invitation within the last 400 days, or where the account has remained inactive after accepting an invitation during that time. Users with such accounts will not be notified by email before deletion. This step is aimed at reducing the security risks associated with dormant accounts and is part of the preventive measures to increase digital security.